A prospective, interdisciplinary study will be continued concerning immunologic response of children in whom postpericardiotomy syndrome develops. Objectives are to (1) identify pathogenesis of the syndrome, (2) learn whether there is a correlation between clinical manifestations and circulating antibodies against myocardium and certain viruses, (3) develop a specific diagnostic test, (4) determine optimal management and (5) if possible, prevent the complication. Our studies on a triple-blind basis in 289 children undergoing intrapericardial procedures indicated a correlation between the presence of syndrome, which occurred in 27% of subjects, and high titer of heart-reactive antibody determined by immunofluorescent technique, and a fourfold or greater rise in complement-fixing antibody against one or more of eight viruses. We propose to expand that study to include adults undergoing intrapericardial surgery or sustaining myocardial infarction, and patients with pericardial trauma to learn whether the same associations occur after surgery in adults as in children and in the other two clinically similar syndromes in a different setting, the postmyocardial infarction and postpericardial trauma syndrome. We shall evaluate at prescribed intervals clinical syndrome in the patient and concurrently measured serum antibody against myocardium and 13 specific viruses. Heart-reactive antibody will be determined by radioimmunologic as well as immunofluorescent techniques for confirmation and quantification of response. To test the possibility that cellular hypersensitivity to cardiac antigens plays a role in the syndrome, migration-inhibition studies of peripheral blood lymphocytes and measurement of stimulation of DNA synthesis by sensitized lymphocytes, tested by incorporation of 14C thymidine will be done. Cytotoxicity of heart-reactive antibody will be tested in 51Cr-labelled, cultured cardiac cells. To characterize the heart-reactive antibody, antibody eluted from an antigen-antibody aggregate will be tested as to immunoglobulin class and subtype and for components of myocardial tissue against which it reacts. Clinical management will be standardized and will not be altered until sufficient clinical immunologic, and virologic data have been collated to permit a judgment as to etiology and possible trial of therapeutic intervention or prevention.